While looking at customizing some home page content (including the Announcements summary web part), I came across this little gem describing how to do things like remove the By and Modified date from the display. It involves using SharePoint Designer to customize the page containing the summary web part, editing the XML that controls the display. Not very user friendly, but I tried it and it gets the job done. If you know of a better way to do this, speak up.
For instance, to remove the By section, do a search in the code for the following and remove it:
></HTML><HTML>by </HTML><Field Name="Author"/><HTML><![CDATA[</td><td width=20% align="]]></HTML><HTML>right</HTML><HTML><![CDATA[" nowrap class="ms-vb">&nbsp;]]
Thanks, Cory, whoever you are!